Topographic Maps & Gradients — Drills · Grade 9 Science

Chapter: Investigating Earth

What these drills covers

By the end of Topographic Maps & Gradients you should be able to:

8 questions, numeric, written answer and multiple choice, each with a worked explanation.

Vocabulary used: contour, contour interval, gradient.

Problem 1

Contour values are 100, 120, and 140 m. Find the contour interval.
Answer and explanation

20 m

Successive values differ by 20 m.

Problem 2

Which way does the V formed by contours crossing a stream usually point?
Answer and explanation

Upstream, toward higher elevation.

Problem 3

Contour lines close together indicate
  1. gentle slope
  2. steep slope
  3. flat ground
  4. a depression
Answer and explanation

steep slope

The same height change over a shorter horizontal distance means a steeper gradient.

Problem 4

Two points differ by 120 m in elevation and are 4 km apart. What is the gradient in metres per kilometre?
Answer and explanation

30 m/km

120 / 4 = 30 m per km.

Problem 5

A contour interval is 20 m. How many metres does crossing 7 contour lines uphill represent?
Answer and explanation

140 m

7 × 20 = 140 m of elevation gain.

Problem 6

Contour lines that form a closed loop with hachure marks pointing inward show
  1. a hill
  2. a depression
  3. a river
  4. a road
Answer and explanation

a depression

Hachures indicate ground falling inward rather than rising.

Problem 7

Explain how contour lines reveal the direction a stream flows.
Answer and explanation

Contours bend upstream where they cross a valley, forming a V that points toward higher ground. Since water flows downhill, it runs in the opposite direction to the V's point. Reading several crossings along the channel confirms the direction without needing any elevation figures.

Response criteria

  • State a scientifically accurate conclusion.
  • Show the data, mechanism, or calculation that supports it.
  • Include units, conditions, or limits where relevant.

Problem 8

Why can two maps of the same area look very different?
Answer and explanation

Scale and contour interval change what can be shown: a small interval reveals gentle features that a large one hides, and a larger scale allows detail that a small scale must generalise away. Purpose also matters, since a geological map shows rock units and a topographic map shows shape. Comparing maps therefore requires checking the scale, interval and purpose first.

Response criteria

  • State a scientifically accurate conclusion.
  • Show the data, mechanism, or calculation that supports it.
  • Include units, conditions, or limits where relevant.

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